The NodeList.keys() method returns an iterator allowing to go through all keys contained in this object. The keys are unsigned integer.
Syntax
nodeList.keys();
Return value
Returns an iterator.
Example
var node = document.createElement("div"); 
var kid1 = document.createElement("p"); 
var kid2 = document.createTextNode("hey"); 
var kid3 = document.createElement("span"); 
node.appendChild(kid1); 
node.appendChild(kid2); 
node.appendChild(kid3); 
var list = node.childNodes; 
// Using for..of 
for(var key of list.keys()) { 
   console.log(key); 
}
The result is:
0 1 2
Specifications
| Specification | Status | Comment | 
|---|---|---|
| DOM The definition of 'keys() (as iterable)' in that specification. | Living Standard | Initial definition | 
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari | 
|---|---|---|---|---|---|
| Basic support | 51 | 50 (50) | No support | 38 | 10 (maybe prior) | 
| Feature | Android | Android Webview | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android | 
|---|---|---|---|---|---|---|---|
| Basic support | No support | ? | 50.0 (50) | No support | ? | 10 (maybe prior) | 51 |